Art of recording sounds



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July 27 1926. 1,593,735

F. K. VREELAND EI' AL ART OF RECORDING SOUNDS Filed March 14,` 1919 2Sheets-Sheet l wx@ July 27 1926.. 1,593,735

1 F. K. VREELAND Er AL ART OF RECORDING lSOUNDS Inventar a l W/u. `7 z omg mcd-...4%

flatenteol .lluly 27, lQ

entre' erstes Nie/airsur idearceo FREDERICK K. VREELND AND FRANK L.DYER, 0F MNTLAIR, NEW JERSEY.

MT @1F RECORDING' SOUNDS.

.application illedl March 14, 1919. Serial No. aalo.

Our invention relates to various new and useful improvements in the artof recording sounds.

As sound records are now made it is the 5 practice to receive'all thesounds in a single recording device, generally in a single horn and bymeans of a single diaphragm connected mechanically tothe cutting orrecording stylus. Errors and distortions are l0 inevitable inthe makingof these records due to nthe natural resonance of the diaphragni and ofthe horn, which amplilies and distorts certain sounds. At best theresult is a compromise,vdisturbing effects be' ing'minimized as muchaspossible by the skill of the operator. Usually, after determining whatthe selection shall be and arranging for its length and t-empo tocorrectly occupy the record, a few bars are played, 'the sounds beingthus recorded, and the test so made is listened to by the director. Thena correction is made; perhaps, some of the instruments may be shiftedWith rcspoot to others or with respect to the horn or special directionsmay be given to certain of the musicians to try for somedifferent/effect, or in the case of a vocal selection special directionsmayf he given to the vocalist to change his position respecting the hornor to control his voice in some special way; and thereupon another testis made of a few bars,wl1ich is again listened to by the director. Thesetests are repeatedA over and lover again, some times for hours at atime, the instruments being shifted back and forth until the recordis aswell balanced as possibfe, and thereupon a finished master is produced.The making of these tests is necessarily expensive and extremelyharassing to the musiciansy and the greatest pains are required on thepart of every one.

Furthermore, at the resent time, the sounds which are recor ed arerelatively loud for the musicians and some times as many as six or morevocalists are crowded together into la comparatively small room. Thisexaggeration is... necessary because the present recording devices arerelatively in sensitiVe. Moreover, the effectiveness of a recordingdiaphragm very rapidly falls olil as the source of the -sounds recedesfrom the recording device. for example, a sound, which to the ear maynot be 'unpleasantly loud if ten vfeet from its source, may still beclearly heard 100 feet away, yet in the case of a recording diaphragmthe samesound might be effectively recorded at a Therefore, theperformance of a selection as carried on in a recording laboratory haslittle or no resemblance to its performance under proper musicalconditions in a concert hall for example; there is not the same balance;certain instruments may be played very much louder and other instrumentsvery much `less loud. Some instruments, for instance violins, areentirely remodeled to give a proper simulation of the sounds to berecorded, While other instruments, like the piano, have never beensatisfactorily recorded. All of these difficulties and defects areobvious to persons havingy an educated musical sense and are manifestedin the records themselves. Thel fact that these records are as good asthey are is due very largely to the skill and experience of thedirectors who have charge of their making andWho have learned throughyears of experience how to get the best results from the crude andinetticient apparatus with which they Work.

With our improvements, it is possible to make records of veryfaintsounds, so that it is not necessary to do the recording in a smallroom nor is it necessary that all the performers shall be crowded aroundthe single recording device. Records, in fact, may be .made in a concerthall or theatre of the music as it is heard directly by the ear. Soundswhich cannot be recorded at all under present conditions may be recordedby vmeans of our improvements, such as the singing of birds or thespeech of an orator, who may be a vsubstantial distance awa from therecording apparatus, or a theatrical or operatic performance, Where itmay be impossible to have the recording device on the stage. f v t Oneof the obstacles at the present time to combining the talkingmachine-With moving pictures, is the great difficulty of making therecords sufficiently loud, andconsequently'the available space in whichan action to be-recor'ded takes place is necessarily greatly limited.But by means of our improvement sufiiciently loud records maybe made,even `though the source of the sounds is located ya substantial distancefrom the recording apparatus.

. We effect these results by causing the sounds to be recorded toactuate a telephonie transmitter or microphone by which the sounds willbe converted into current waves and we amplify these waves by 4means ofone or more amplifiers, preferably of the electron relay type, and theamplified :waves are then caused to 4actuate a magnetic receiver which ocrates the cutting or recording stylus. y using -a series of suchamplifiers operating successively, anyydesired degree of' amplificationmay be imparted to the current wavescorresponding to the sounds to berecorded and without distortion; in fact, it Vis possible in-this way toamplify sounds 'to a sufficient exten-t to make a record thereof whenthose sounds Aare practically inaudible. These and many other remarkableresults are made possible by the fact that :the enf ergy required tooperate the recorder 'is not derived directly from the sound waves, butlfrom -a local source of energy controlledby those waves. Thus soundwaves of very feeble energy may be used to make a record of any desiredintensity without distortion.

Tith our improvements, it is possible'to secure any desired relation ofinstruments or vocalists to secure -the proper balance, without loss of'time in making repeated tests, as at present. We eect this result vbymaking use of a plurali-ty -o-f microphones or other transmitters whichmay be readily moved from place to place so as to occupy any desiredposition with respect to the orchestra or Vocalist, -all feedin currentwaves to the magnetic receiver, an we provide a separate listening phonewhich the director may carry on his head and which excludes directsounds. Therefore, the,di-rector can listen to the sounds exactly asthey are to be recorded and can ldirect his assistant where to placeythe several `microphones with respect 'to the musician or vocalist,and, if: necessary, -give'his directions to the musician .or vocalistwhereby certain desired effects shall 'be secured, all without vthe needof making any test whateverand without wasting any time. Thus, themusicians may play-through the entire selectionjand .not -merely a few"bars thereon-.during which time the director by causing the microphonesto 'be shifted in various ways may secure what he considers .to fbe theproper fbalance. 1021` the .desired balance may be secured withoutmoving the Ignoro hohes 'by adjusting vtheir respective ampli cations.

"The composite currents :from .the several microphones all feed :into acommon receiver circuit and thus actuate the recorder magnet `with ayresuittam. .effect ydue not to iany crophone. Means are 4preferablyemployed for controlling the degree of am-pl-ication, all of which maybe located near the director, who, by means of his listening phone,

.may himself thus control the .recording to a large extent to secure thedesired effect. In this 4way also, the .director can have .in hiscontrol the vocal sounds-,produced iby en Iartist and can properly 'cut.them 'down if rtoo loud or amplify vthem if not floud enough, Whereasat the present time, in such an event the director must signal .theartist to recede from or approach the. horn. In fact, in many cases atpresent the director stands with his hand on the artists shoulder andpushes him forward or hack, l.towards .or away from the horn as .hisjudgment may indicate, but he has no means of knowing what the resultmay be until a .test is made from the actual record. With ourimprovements, the director at all times by lmeans .of the listeningphone knows precisely .the relation between the vocal sounds and the instrumental sounds, and has means for stant control or adjustment.

lVith our improvements, we are able .to substantially reduce thedistortions now due to resonance in vthe recording diaphragm, which, asis well known, 4produces peaks or amplification corresponding to certaintones. This result is achieved. 'when a number of -diaphragms are usedby making the daphragms dissimilarwsuch as .of different size orthickness of material-so that the resonance points will not correspond7and hence the recorded sound will not be characterized by such extremedistortions as'wlmn a Single recording diaphragm is used. The sanmeefrfeet can be .secured .minimizing-thc distortion due ,to horn resonance,lthatis 'to say anumber of dissimilar horns may be employed whereby theresonant periods of one will not .correspond :with those'of any other.Or thea 'horns may be omitted altogether, since vany desired recordintensity may b e secured without them.

In order that our invention may be better understood attentiau isdirected 'to .the accompanying drawings forming .a part otf'thisspecification, and in which Fig. 1 is a dla' gram showing vour inventionas :carried out with a single microphone and two successive.- lyoperatmg electron amplifiers. Fig. '2 .a

diagram-showing the invention as :used with lliU weaves four microphonesall'feeding into a common parallel circuit with a single amplifier and alistening phone in the circuit of the magnetic recorder. F ig'. 3, acorresponding view showing three microphones, sach having' an electronamplifier, and with the controlling devices for regulating theamplification all located near a common point so as to be within thecontrol of the director.- Fig. ll, sectional views showing threeseparate diapliragms and three separate horns, the dissimilarity of thediaphragme being secured by varying their diameter and the dissimilarityof the horns being secured by varying their size. Fig. 5, acorresponding View showing three dissimilar diaphragme, thedissimilarity being secured by varying the thickness of the diaphragms.Figs 6, 7 and 8 represent conventional curves of response of threedierent diaphragms to sound waves of different frequencies showing thepeaks due to resonance of the diaphragms, but the peaks correspondin tonotes of dierent pitch in the three diaphragme. The three curvesindicate that the sounds represented thereby were of substantially thesame amplitude. Curves of response of this general character are shownvat a, b, c .in Fig. 117 (page l14:9) of a book entitled The Science ofMusical Sounds by lDa ton C. Miller (New York; 'llhe McMillan o., 1916).According to this book the three curves in Fig. 117 represent theresponses of three glass diaphragms of 22, 31 and 50 millimetersdiameter, respectively. Fig. 9 is a composite diagram illustrating theeffect of combining the current waves produced by the three diaphragmsof Figs. 6, 7 and 8 respectively, illustrating how the distortion isreduced by such combination. Fig. 10, a detail view illustrating adistortionless magnetic receiver or recorder, without'a diaphragm. lnall of the above, corresponding parts are represented by the samereference numerals.

Referring first to Fig. 1, the microphone or other transmitter 1 is ofany suitable standard type, being provided with a horn 2 of any suitablematerial for collecting the sounds and directing them to the mouth pieceof the microphone. rllhe michrophone and horn should be designed foraccurate rendering of tone values rather than for high sensitivity, asany desired intensity of record may be secured by the amplificaion. rlhecurrent waves from the microphone, by means of transformer coils 3, 3',are fed to an electron amplifier li, having familiar circuitconnections, by which the current waves will be amplified. From thisamplifier, by means of' coils 5, 5', the amplified current waves aredirected to a second amplifier 6 where a further amplicaion takes place.Obviously as many of these amplifiers may ,be ein. loyed as may be.needed to` secure the desired degree of amplification. From the lastamplifier in series, by means of coils 7, 7 the amplified current wavesare fed to a receiver circuit 8, in which is located a magnetic recorderwhose coils 9 actuate a diaphragm or armature l0, which operates thelink 11, to which is connected the cutting or recording stylus 12, whichimpresses the record on a disc or cylinder of recording inaterial. nFherecord may obviously be of the laterally undulating or verticallyundulating type. vit will be seen that sounds received by the microphone1 will be amplified by the amplifiers 4 and 6 and that the amplifiedcurrent waves will actuate the magnetic receiver and cause the cuttingor recording stylus to be actuated in accordance with the originalsounds, but to any desired ampli-l fied extent depending upon the degreeof ainplification.

Referring to Fig. 2, we show four microphones all feeding in parallel toa common receiving circuit. Thus this receiving circuit will beinfluenced by the current waves from all the microphones. The compositecurrent thus developed will be amplified by the electron amplifier andthe amplified composite current will flow through the receiving circuit8 to actuate the magnetic recorder. It will, of course, be understoodthat instead of using a single amplifier 15 a plurality of suchamplifiers may be einployed for amplifying the composite current, asillustrated in Fig. I1. 16 represents a listening phone connected to thereceiving circuit 8. This listening phone maybe carried by the directorand is preferably arranged to exclude direct sounds, so that thedirectormay listen at all times to the resultant sound waves from allthe microphones which influence the magnetic receiver. The severalmicrophones 1 (Fig. 2) are preferably movable from place to place, sothat they may be located at any desired pointsv with respect to theorchestra or vocalist. The director gives his directions to hisassistants as to where these microphones shall be placed, so as tosecure the required balanced effect as Vwill be understood,

Referring to Fig. 3, we show three micro-' phones, each provided with aseparate electron amplifier 17 by which the current waves from eachmicrophone will be amplified. .Through transformer coils 18, 19 and 2Oshown as arranged in series, these amplified current waves are fed tothe receiving circuit 8 so as to influence the magnetic recorder. Thelistening phone 16, as in Fig. 2, is connected to the recorder directlyso that it will be influenced by the composite amplified current fromall the/microphones and the director may thus know exactly what is beingrecorded. The potentiometers 21, 22 and 23 of the several microphonesare all located near a common point within reach of the director, sothat he may himself control the :degree .of amplification ofv one-'orall of the microphones. Preferably the dia phragms of :the microphones.are-iliade purposely dissimilar; forA example, by varying theirdiameter, .as shown at Fig. t, or by varying their thickness, as shownlat Fig. 5, and referably also the horns :are made purpose y dissimilar;for example,- by varying their size as shown at Fig. 4.' The importanceof using dissimilar diaphragms and dissimilar .horns will be obviousfrom in-v spection'of Figs. 6, 7 and 8, which show the curves ofresponse of diaphragme of diii'erent ldiameters. With' these diaphragmsit Will be noted that peaks are formed, "corresponding to certain tones,.andrepresenting abnormal increases in amplitude. Ifq therefore, anordinary recorder were used with a diaphragm having the characteristicsof Figure G, Whenever a sound is'recorded corresponding 'to itsresponsive toiie,z=orI in its immediate neighborhood, it *will begreatly Kdistorted in the record'.

By the use of the present invention, com

. binillg thelresponses of .the three -dvkphagins to cause them tofeed'the vcurrent Waves into a common circuit, the resultantyintluencingthe magnetic receiver, will correspond to the diagram of Fig. 9, 'inwhich it `will bef'ncted that the peaks are relatively diminished.. In

, other 'vv/orde, in the case of the individual diaphragms'the peaksrepresent a distortion in amplitude of'substantially one hundred percent, Whereas When L. the :effects of the three diaphragms are combinedthe peaks .as shown in Fig. 9 represent a distortion of only aboutthirty-three per cent. It Will be understood that by employing aseparate amplier for the several transmltters as shown in Fig. 3, theamplitude ofthe curves cfresponse from such diaphragme .maybe brought toany desired value so as thereby to secure .the best effects due to thecombination of currents from the three diaphragme in reducing thedistortion due to resonance'. In other Words, if three curves ofresponse, |corresponding to a, b 'and c in Professor Millers book, arecombined, the curve c is ofsormnch greater amplitude than of a vor thatthe combination of the three gives a vvery' slight increase in thegeneral body of the tone, but by amplifying lelectrically the responsesof yc and b to bring these curves up to va value comparable to that ofc, the beneficial effect described willl be secured. The same thing istrue in the case ofthe horn, which, as `is well known, also has naturalperiods of resonance, but by using dissimilar horns thesel resonantpeaksk may be flattened out i-n the same Way as when using .dissimilardiaphragms. Or the horns may be omitted altogether, depending on theamplifiers to give the requisite reco-rd intensity. Orf course, whenonly three micro'- phones are used there may still be 'su-losta'nf tial.peaks 4o1" simplifications due to rescnance, but by using aconsiderable number of .microphones .for instance eight or ten, thesedisturbances due to resonance may be practically eliminated so as not tobe detected in :the finished record.

inasmuch as the Vin'otioifi ofthe recorder stylus isv controlled, not`by .direct mechanical action of sound Waves but by an electric current,it is not necessary to use a diaphragminthe'recording apparatus. The

'recorder stylusimay vbe operated by any suitablc device capableoftranslating an electric current into motion. @It is thus possible to usedevices Whose laction Iis remarkably free vfrom distortion ofthe Waveform. For ex4 ample, the amature of the recorder magnet may be `carried.by any suitable yielding sup porting means, such 'as a spring. Thissupporting means should "be such that it Will not. give the armature 'anatural, vibration period Within the .audible limit.

One form ofV recorder is shown in Fig. 10, and'comprises an armature 10carried by a stretched Wire 2s, operating the ystylus 12 through thelink 11. The stretched Wire 24 is providedorvit-h a screw 25 for:adjusting its tension. By making the armature light and the tension ofthe elastic Wire relatively high the natural period of vibration of thedel vice may be ymade above the limit of audible sound, so the responseof the recorder to sound vibrations will be practicallydistortionless.-`

Obviously it is not necessary to use microphones for picking up thesound Waves. Any suitable form of'sound-responsive electrical generatoror transmitter may be used:

for example., an electromagnetic transmitter, in which the motion of aydiaphragm relative to a magnet produces current vibrations in thelmagnet coil through variations 4in the reluctance of thev magneticcircuit.

Such ldevices possess certain advantages, for although less sensitivethan microphones they may be made exterem'ely free from Wave formdistortions.

The yexpression cutting or recording stylus, as used by us in thefollowing claims, is intended to refer to a device having the capacityof bodily.k removing lthe material of the blank on which the record isAformed y lor indenting or displacing the blank material in theformation of such record, or the making of a record by the injection ofan extremely attenuated Wax thread on a metallic surface, -or themakingof 4the record magnetically in steel,'as proposed by Poul sen,.by thedirect action of za magnet operated by the amplified currents or in-aiyother suitable Way, our invention not resi ing in details having to dowith the physical formation of the record butonly with the means bywhich the record forming device is l llO - mear-3s Having now describedour invention, what we claim as new therein and desire to secure byLetters Patent is as follows:

'combination of a plurality of telephonie l. In the artof recordingsounds,'theco1 n bination of a series of telephonie transmitters forreceiving the sounds to be recorded tude ofthe current Waves from eachtransmitter, and a receiver operating the cutting or recording stylusand actuatedby the-cur-` substantially/ as set forth.

rent waves from the several transmittersyfI mitters for receivin thesounds to /be VreH corded and converting them into current"l Waves,meansfor separately controlling the] amplitude of the current Waves fromeach, transmitter, a lreceiver operating the cut' bination of aplurality of telephonie transmitters for receiving the soundsto berecorded and converting them into current waves, said transmitters beingseparately movable With'respect to the source of said sounds, and areceiver operating the cutting or recording stylus and actuated bythecurrent Waves from the several transmitters,

' substantially as set forth.

4. In the art of recording soun ds, thecom'-V bination of a plurality oftelephonie trans- `mitters for receiving the sounds tobe re'- f cordedand converting them into -current waves, said transmitters being.separately-' movable with respect to the source dt-said;

sounds, a receiver operatingthe cutting or listening phone alsoactuated'by the. current corded and converting themtw'intofcurrentcurrent Waves in eac transmitter, and aree stylus and' actuated by thecurrent Waves from the several transmitters, substantially as set forth.f

6. In the art of recording sounds, the

transmitters for receiving the sounds to be recorded and converting themi-nto current waves, said transmitters being separately movable withrespect to the source of said initt I- 1rl "In 'theart of recordingsounds,'the COll v"trans istics for receiving sounds to be recorded' sof telephonictraIis- Amitters for receiving the" sounds tob-e resthesounds lto be recorded sounds, -means for separately controlling the lcurrent Waves from each transmitter, said 'v 'Controlling means beinglocated near a commonr point, and a recel er operating thecutcombination of a plurality of telephonie transmitters for receivingthe sounds to be 'recorded andconverting them into current waves',-sa'id transmitters -being separately f movable .with respect to thesource of said 2. In the art of recording sounds, the com-4*V binationof a plurality of telephonictrans-"L sounds, means for separatelycontrolling the v current Waves from each transmitter, said controllingmeans being located near a com- `monj,pointa receiver operating thecutting orgrecording stylus and actuated by the cur- Irentfvvaves fromlthe several transmitters, .and 'a listening phone located in proximitytovsaid-controlling means and also actuated bythe current Waves from theseveral-transers, 1substantially as set forth.

nation of a plurality of telephonie initters of `different resonantcharacterand converting them into current waves and a receiver'operatingthe cutting or recording. stylus and actuated by the current waves fromthe several transmitters, substantially as set forth.

p9.In the art, of recording .-sounds, the

'. combination of a plurality of telephonie transmitters of differentresonant character- "ist-ics for receiving sounds to be recorded andconverting them into current Waves, an electron amplifier for amplifyingthe Acur'- rrent Waves,. -and a receiver operating. the

cutting or recordingstylus and actuated by the current .Waves oftheseveral transmit# n ters, substantially as set forth. recording stylusand actua ted-by the current,

Waves from the several transmitters`,and a;

10;"'In the art offrecording sounds, `the combination of a' .pluralityof., telephonie transmitters of different resonant characteristics forreceiving the sounds to be recorded= `and convertingthem into currentwaves, .an velectron vamplifier .for amplifying the #current --waves,kmeans for controlling the amplifying effectof the amplifier, and a revceiveroperatingl the cutting or `recording Waves,sa1d transmittersbeingIv separately. movable With respect to the; source of said lsounds, means for separately'lcfontrolling the 55 `ceiver operating thecuttingjor recording stylus and actuated by the ,current Waves from theseveral transmitters, substantially as set forth.

12. In the art of recording sounds, the

i zo

combination of a 'pluralty of telephonie ing stylus-and sebum-.ed bythe-current Waves transmitters, having diaphragms of differ of theseveral transmirtbars, substantially @s ent resonant characteristics forreevng set forth. 10 the sounds to 'be rerded and aanval-ting Thisspeeeatiou Signed and witnessed 5 them into current waves, im electron,ampli this 13th day ai March, 1919.

fier for amplifying the current Waves, and FREDERICK K. VR'EELAND, areceiver operating the `cliff/ting or recurrir FRANK L. DYER.

